bugfix gflow-finding algorithm

[shinich1]

Before submitting, please check the following:

• Make sure you have tests for the new code and that test passes (run tox)
• format added code by black -l 120 <filename>
• If applicable, add a line to the [unreleased] part of CHANGELOG.md, following keep-a-changelog.

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Context (if applicable): closes #95

Description of the change:

• fixed gflow and flow finding part of visualisation tool.
• bugfix GF2 data treatment in gflowaux

Related issue:

also see that checks (github actions) pass. If lint check keeps failing, try installing black==22.8.0 as behavior seems to vary across versions.